Electron discharge device envelope structure providing a radial force upon support rods



Sept. 6, 1966 J. M. SCOTT 3,271,614 ELECTRON DISCHARGE DEVICE ENVELOPESTRUCTURE PROVIDING A RADIAL FORCE UPON SUPPORT RODS Filed Aug. 18, 19615 Sheets-Sheet l WITNESSES INVENTOR John M. Scorr fl/a yfi v m ATTORNEYSept. 6, 1966 J. M. SCOTT 3,271,614

ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PROVIDING A RADIAL FORCEUPON SUPPORT RODS Filed Aug. 18, 1961 5 Sheets-Sheet 2 Fig.4.

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Sept. 6, 1966 J. M. SCOTT 3,271,514

ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PROVIDING A RADIAL FORCEUPON SUPPORT RODS 5 Sheets-Sheet 5 Filed Aug. 18, 1961 United StatesPatent 3,271,614 ELECTRON DISCHARGE DEVICE ENVELOPE STRUCTURE PRQVHDINGA RADIAL FORCE UPON SUPPORT RODS John M. Scott, Linthicum Heights, Md.,assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, acorporation of Pennsylvania Filed Aug. 18, 1961, Ser. No. 132,371 6Claims. (Cl. 315-3.5)

This invention relates to electron discharge devices and moreparticularly to microwave tubes of the traveling wave type.

Discharge devices of the class described herein generally comprise anelongated evacuated envelope with an electron beam producing meansdisposed at one end thereof for the production and projection of anelectron beam along a predetermined path within the envelope and a slowwave propagating means, usually comprising an electrical conductor inthe form of a helix, for propagating electromagnetic waves along thelength of the envelope in an interacting relationship with the electronbeam. In relatively high powered tubes of this type, considerable heatis generated within the helix by beam interception and radio-frequencylosses. As the temperature of the helix rises, so too does itsresistance with a resulting diminishment in the radio-frequency poweroutput of the tube. Further, in some tubes, this heating effect may beso great as to completely destroy the helix or other slow wavestructure. It is essential, therefore, that adequate means be providedfor removing the generated heat from the helix.

Accordingly, it is the general object of this invention to provide a newand improved traveling wave tube.

Another object of this invention is to provide an improved envelopestructure for a traveling wave tube.

A further object of this invention is to provide a novel multiplesegment envelope for supporting the slow wave structure of a travelingwave tube in an eflicient heat transfer relationship with the envelope.

Briefly, the present invention accomplishes the above cited objects byproviding a multiple segment envelope in a traveling wave tube forsupporting the slow wave propagating means. This structure permits theadjustment of the slow wave structure within the envelope and ensuresbetter contacts between the helix, support rods, and envelope to providea more efficient heat transfer path from the helix to the envelope.

Further objects and advantages of the invention will become apparent asthe following description proceeds and features of novelty whichcharacterize the invention will be pointed out in particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to theaccompanying drawings, in which:

FIGURE 1 is a schematic representation showing a traveling wave tubeembodying the present invention;

FIG. 2 is an exploded perspective view of the envelope of FIGURE 1showing one embodiment of the invention;

FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 1;

FIG. 4 is an exploded perspective view showing a step in the manufactureof the envelope shown in FIG. 3;

FIG. 5 is a cross-sectional end view showing a second step in themanufacture of the envelope shown in FIG. 3;

FIG. 6 is a fragmentary exploded view showing an assembly feature of thepresent invention;

FIG. 7 is a cross-sectional view of a modification of an envelope inaccordance with the present invention;

3,271,614 Patented Sept. 6, 1966 FIG. 8 is a perspective view of thepreferred embodi-- ment of this invention; and

FIG. 9 is an end view of a modification of the embodiment of FIG. 8.

With specific reference to FIG. 1, there is shown, by way of example, anelectron discharge device of the traveling wave tube type whichcomprises an elongated, evacuated envelope 11 which is of constantcross-sec tional area and is made of suitable material such as copper ormolybdenum. At one end of the envelope 11, and disposed within anenlarged portion 13 which may be made of glass and which is hermeticallysealed to the envelope 11, is an electron beam source, indicatedgenerally by the reference character 2. This source comprises anelectron emissive cathode 17, a focusing electrode 19, and anaccelerating electrode 21. These elements are connected to suitablesources of voltage, which have not been shown, and collectively act todirect a beam of electrons centrally along the axial length of theenvelope 11 to the opposite end of the envelope at which point islocated an electron collector 23. The collector 23 is positionedtransversely to the electron beam within a second enlarged glass portion15 located at the opposite end of the envelope 11 from that of theelectron gun assembly and is hermetically sealed thereto. The collectoris also connected to a suitable source of voltage which is not shown. Aslow wave propagating means 25, for the propagation of radio frequencyenergy is disposed centrally within the envelope 11 for the majorportion of its axial length and is coaxial with and in an interactingrelationship with a major portion of the electron beam. The propagatingmeans comprises an electrical conductor usually in the form of a helix,which helix may be single-wound, cross-wound or bifilar-wound and may beof wire, tape, or of other configuration in accordance with goodengineering principles. Electromagnetic energy may be applied to thehelix or lsow wave propagat ing structure by means of a coaxial cable 29which extends and is sealed through the side of the envelope 11, or byany other suitable electrical network. A second coaxial cable 31 isprovided at the opposite end of the helix for the removal of radiofrequency energy from the helix.

The helix 25 is supported within the envelope 11 by a plurality ofsupporting members 27 which are disposed along the axial length of theenvelope for substantially the entire length of the helix. As is shownin FIGS. 3 and 7, these supporting members 27 are substantially keystoneshaped in cross-sectional area (although they may be of circular orother configuration) and are made of a suitable heat conducting,electrical insulating ceramic such as alumina or beryllia. While fourequally spaced keystone support members are shown in the drawings, thisnumber is not critical and the number of supporting members and theirrelative spacing about the helix may be varied as the individual casemay require.

In order to prevent the electron beam from spreading to such an extentthat it would pass out of the interacting region and possibly interceptthe slow wave propagating means, it is necessary to provide some form offocusing means. Focusing in the present instance is provided byproducing a magnetic field axially along the envelope structure. Thisfield is achieved by providing a long annular solenoid 33 whichsurrounds the envelope for the entire length of the helix 25. Tosimplify the present drawing and description, the magnetic fieldproducing solenoid 33 is only schematically illustrated and the sourceof energization is not shown.

With reference to FIGS. 2 and 3, there is shown one embodiment of theinstant invention. The envelope 11 of FIG. 1, as shown in thisembodiment, comprises two trough or channel shaped members or segments11a and 1112 having mating longitudinal edges 43 and 45, respectively.Segment 11a is provided with a pair of upstanding flange portions 35which extend longitudinally along its inner radius. Segment 11b islikewise provided with a pair of upstanding flange portions 37 whichextend longitudinally along its outer radius. These two pair of flangeportions abut one another along their length and co-act to assure theproper alignment of the segments 11a and 11b as is best illustrated byFIG. 3. Keyways or depressed portions 39 may be provided in the interiorsurface and along the axial length of the envelope 11 to more accuratelyand securely locate the support rods 27, the number of keyways beingequal to the number of support rods.

The preferred method of constructing the two segment envelope structureis shown in FIGS. 4 and 5. A first block of envelope material 11b ismachined to form a central recessed portion 57 as is illustrated in FIG.4. A second block of envelope material 11a is machined to form a centralupstanding portion 59 which is of such dimensions so as to closely fitwithin the recessed portion 57 of block 1112. Small longitudinal slots,51 and 53, are machined into each of the blocks 11b and 11a,respectively, to provide a center hole for drilling purposes, as will beexplained later. The blocks 11b and 11a are easily machined, for exampleby milling, to great accuracies to ensure a close mating structure.After the blocks have been machined as above, they are fitted togetherand held in place by suitable clamps 49 (FIG. 5), and the center bore55, which forms the cavity into which the helix is placed, is now formedlongitudinally through the blocks 11a and 11b. The preferred method offorming this bore is by gun drilling, i.e., rotating the drill in onedirection and the work piece in the opposite direction, with the slots51, 53 acting as a centering hole. After the center bore 55 has beenformed, the outside of the envelope may be shaped to the desired form inaccordance with the method of focusing and/or cooling system to be used.In the present embodiment (FIG. 2), the outside of the envelope iscircular in shape. The envelope segments may now be separated and thekeyways 39 machined, for example by milling, into the inner surface ofthe envelope.

FIG. 6 illustrates one method by which the two piece structure of thepresent embodiment may be used to increase the contact pressure betweenthe helix 25, support rods 27 and envelope 11. As the lack of sufficientcontact pressure is the greatest source of resistance to heat flow fromthe helix to the envelope it is important that this pressure beincreased to an extent suflicient to offer a low resistance heat path.By the use of the two piece structure of the instant invention, theassembly within the envelope 11 may be adjusted to increase the contactpressure before the final assembly is made. This adjustment may be inthe exchange of components such as substituting one supporting rod 27for another which may be of slightly different size. A furtheradjustment may be the substitution of one helix for another. Smallquantities of metal may be removed from the keyways or shims 47 ofdesired length and thickness and made of a suitable heat conductingmaterial, such as copper, may be added. These adjustments may be madesingularly or in any combination to ensure good contact pressures andhence eflicient heat transfer paths.

Thus, it may be readily seen, that the multiple piece structure of theinstant invention allows for the ready adjustment of the internalstructure within the envelope to assure sufiicient contact pressure atall points to provide an efiicient heat conducting path from the helix25 through the support rods 27 to the envelope 11.

After the final adjustment of the internal structure has been made, theenvelope with its internal structure may be placed in a suitable jig,which has not been shown, and

4. the braze 41 made along the mating edges 43, 45 to mechanically joinand hermetically seal the envelope 11.

FIG. 7 shows a modification of the invention which differs from thatshown in FIGS. 2 through 6 only in that the self-aligning featureoccasioned by the upstanding flanges 35 and 37 is not present. Whilethis embodiment does not provide for the self-alignment, it does permitthe adjustment of the internal structure within the envelope 11 prior tothe brazing operation. From this, it is evident that the nature of thedivision of the envelope members is not critical but in fact can be madein a number of ways. It is also evident, although it has not been shown,that the envelope 11 may be made in more than two pieces.

The preferred embodiment of the present invention is shown in FIG. 8.This embodiment comprises a two piece envelope 11 in which the exteriorenvelope wall is non-circular. Each segment of the envelope 11 isprovided with a flange portion 71 which extends longitudinally along thelength of the envelope and which co-acts to form mating surfaces of theenvelope segments. Two or more holes 65 are formed, for example bydrilling, vertically through each of the flange members and pins 69,which may be of the'same material as that of the envelope and whichserve to align the envelope segments are then fitted into each of theholes 65.

Brazing material 41 is positioned in suitable grooves 73 formedlongitudinally along the mating surfaces 75. After the envelope assemblyand necessary adjustments for good thermal contact have been made, theenvelope is heated to a temperature sufficient to melt the brazingmaterial 41 and allow it to flow to effect mechanical bonding andhermetic sealing.

The particular exterior configuration of the envelope 11 is not criticaland as illustrated in FIG. 8 is one which is adapted for water coolingof the outside of the envelope 11. FIG. 9 illustrates the use ofalignment pins in an envelope of circular design. In this instance, theholes 65 are formed in the envelope walls perpendicular to each of themating surfaces 75 of each envelope segment and alignment pins 69 arefitted into each of the holes of one segment. The pins 69 are ofsufficient length to extend into and substantially fill the holes of thesecond segment when the envelope is assembled.

From the above it is apparent that there has been disclosed a multiplepiece envelope which will provide for an improved heat conducting pathfrom the helix 25 to the envelope 11. While there have been shown anddescribed what are at present considered to be the preferred embodimentsof the invention, modifications thereto will readily occur to thoseskilled in the art. It is not desired, therefore, that the invention belimited to the specific arrangements shown and described and it isintended to cover in the appended claims all such modifications as fallwithin the true spirit and scope of the invention.

I claim as my invention:

1. An electron discharge device comprising an envelope, means disposedat one end of said envelope for the production of an electron beam alongthe length of said envelope, electron collecting means disposed at theopposite end of said envelope, slow wave propagating means disposedwithin said envelope for the propagation of electromagnetic energy alongthe length of said envelope, and means inserted between and abuttingsaid envelope and said slow wave propagating means for conducting heatfrom said slow wave propagating means, said envelope comprising firstand second channel members mechanically joined together to exert aradial force upon said means for conducting heat from said slow wavepropagating means, and to ensure an etlicient heat transfer between saidslow wave propagating means and said envelope.

2. An electron discharge device comprising electron beam forming andcollecting means, means for the propagating of electromagnetic energyalong a path coaxial with and in an interacting relationship with saidelectron beam, means comprising at least two segment channels defining acavity for the disposition of said propagating means, means supportingsaid propagating means disposed in an abutting and in a thermal transferrelationship with said envelope, each of said envelope segments beingjoined to form said envelope and to establish a force upon saidsupporting means to enhance said thermal transfer relationship,

3. An electron discharge device comprising an envelope, means definingan electron beam source disposed at one end of said envelope, means forcollecting said electron beam disposed at the opposite end of saidenvelope, means disposed within said envelope for the propagation ofelectromagnetic energy along a path coaxial and in an interactingrelation with said electron beam, said envelope comprising multiplesegments co-acting to form a cavity for the disposition of saidpropagation means, and support members disposed between and abuttingsaid envelope and said propagation means and made of a heat conductingmaterial, said segments being joined together to exert pressure uponsaid support members and said propagation means to insure an efficientheat transfer relationship therebetween.

4. An electron discharge device comprising means for forming andcollecting an electron beam, means for the propagation ofelectromagnetic energy along a path coaxial and in an interactingrelationship with said electron beam, envelope means comprising aplurality of channel segments co-acting to define a cavity for thedisposition of said propagation means, and a plurality of supportmernbers disposed between and abutting said envelope means and saidpropagation means and made of a material having the property ofconducting heat, said segments joined together to apply a radial forceupon said support members and said propagation means whereby anefiicient thermal contact is established between said support membersand said envelope means, and between said support members and saidpropagation means.

5. An electron discharge device comprising means for forming an electronbeam, means for collecting said electron beam, means for the propagationof electromagnetic energy along a path coaxial with and in aninteracting relationship with said electron beam, an envelope comprisinga plurality of mating channel members so as to 45 form a cavity for thedisposition of said wave propagation means, and support members disposedbetween and abutting said envelope and said propagation means and madeof a material having the properties of electrical insulation and of heatconduction, said mating members having depressions to receive saidsupport members, said mating members being joined together to establisha force upon said support members and said propagation means to ensurean eflicient heat transfer relationship between said support members andsaid propagation means.

6. An electron discharge device comprising means for forming andcollecting an electron beam, means for the propagation ofelectromagnetic energy along a path coaxial with and in an interactingrelationship with said electron beam, a plurality of channel segmentsdefining an envelope in which said propagation means is disposed, aplurality of support members disposed between and abutting saidpropagation means and said envelope and made of a material having theproperties of conducting heat and of being electrically insulating, saidsegments having depressed portions for receiving said support members,said segments being joined together to exert a force upon said supportmembers and said propagation means to ensure an efficient heat transferrelation between said segments and said wave propagation means, and heatconductive shims inserted in said depressed portions to abut againstsaid support members and to exert a force upon said support members.

References Cited by the Examiner HERMAN KARL SAALBACH, Primary Examiner.

GEORGE N. WESTBY, C. O. GARDNER, S, CHAT- MON, IR., Assistant Examiners.

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN ENVELOPE, MEANS DISPOSEDAT ONE END OF SAID ENVELOPE FOR THE PRODUCTION OF AN ELECTRON BEAM ALONGTHE LENGTH OF SAID ENVELOPE, ELECTRON COLLECTING MEANS DISPOSED AT THEOPPOSITE END OF SAID ENVELOPE, SLOW WAVE PROPAGATING MEANS DISPOSEDWITHIN SAID ENVELOPE FOR THE PROPAGATION OF ELECTROMAGNETIC ENERGY ALONGTHE LENGTH OF SAID ENVELOPE, AND MEANS INSERTED BETWEEN AND ABUTTTINGSAID ENVELOPE AND SAID SLOW WAVE PROPAGATING MEANS FOR CONDUCTING HEATFROM SAID SLOW WAVE PROPAGATING MEANS, SAID ENVELOPE COMPRISING FIRSTAND SECOND CHANNEL MEMBERS MECHANICALLY JOINED TOGETHER TO EXERT ARADIAL FORCE UPON SAID MEANS FOR CONDUTING HEAT FROM SAID SLOW WAVEPROPAGATING MEANS, AND TO ENSURE AN EFFICIENT HEAT TRANSFER BETWEEN SAIDSLOW WAVE PROPAGATING MEANS SAID ENVELOPE.